This is rather disappointing, after all the hard work you did to get here. There's only one
Mew
, and it's floating in a ball. Simply keep bopping it with items whenever it comes near you, and eventually the Mew will be floating along outside its ball, trying to get back in. You can takes its picture while it does so.

If you're really good, every time you pester Mew while it's out of its
ball, it will be stunned and you can get closer. You might even get close
enough for a big picture with its eyes open!

If you keep bopping the ball after Mew gets back into it, you simply keep knocking it out of its ball again. Nothing else appears, nothing else happens.